Over the last decade, UAVs have become increasingly economical and popular, with advances in lithium polymer batteries, brushless motors and small, low-cost, powerful electronics. UAVs can be used for a wide variety of applications including military surveillance, agricultural surveying, aerial filmmaking and photography, inspection of power lines and pipelines, wildlife counting, enforcement of anti-poaching laws in protected areas, borders patrols, forest fire detection, and search and rescue. Small UAVs can also be useful as personal scouting and safety devices for skiers, hikers, white-water rafters and climbers adventuring in remote backcountry areas.
The multi-rotor is a specific type of UAV with multiple motors and propellers providing predominantly upward thrust to counteract the aircraft's weight, with attitude control being provided by several possible methods including thrust differentiation and tilting of the rotor planes. In an unpredictable outdoor environment or during hazardous missions such as nighttime search-and-rescue, unexpected collisions can occur even when the UAV is under control of a trained pilot or with the use modern collision avoidance systems. In a collision, the exposed spinning blades of a multi-rotor can easily cause damage to a person, object or to the multi-rotor itself. Blade contact with a hard object typically results in a broken propeller or a bent motor shaft. For this reason, multi-rotors are often equipped with propeller guards which may be fixed or detachable (for example as described in U.S. Pat. No. 8,322,648, or as marketed for the DJI Phantom 1), and which form a protective shield around the most dangerous and exposed parts of the blades.
Such propeller guards however are not without their disadvantages. For example, typical propeller guards do not function well with folding-type UAVs, that is UAVs whose rotor arms are movable or foldable into a compact, stored position for ease of transport. With such UAVs the propeller guards first have to be detached from the UAV as otherwise they do not allow for easy transport. There therefore remains a need in the art for new and improved UAVs with propeller guards that at least partially address some of the drawbacks of current propeller guard systems. The present disclosure seeks to provide such a UAV.